Monitoring Anti-tuberculosis Treatment Response Using Analysis of Whole Blood Mycobacterium tuberculosis Specific T Cell Activation and Functional Markers

Background

Blood-based biomarkers have been proposed as an alternative to current sputum-based treatment monitoring methods in active tuberculosis (ATB). The aim of this study was to validate previously described phenotypic, activation, and cytokine markers of treatment response in a West African cohort.

Methods

Whole blood immune responses to Mycobacterium tuberculosis ESAT-6/CFP-10 (EC) and purified protein derivative (PPD) were measured in twenty adults at baseline and after 2 months of standard TB treatment. Patients were classified as fast or slow responders based on a negative or positive sputum culture result at 2 months, respectively. Cellular expression of activation markers (CD38, HLA-DR), memory markers (CD27), and functional intracellular cytokine and proliferation (IFN-γ, Ki-67, TNF-α) markers were measured using multi-color flow cytometry.

Results

There was a significant increase in the proportion of CD4⁺CD27⁺ cells expressing CD38 and HLA-DR following EC stimulation at 2 months compared to baseline (p = 0.0328 and p = 0.0400, respectively). Following PPD stimulation, slow treatment responders had a significantly higher proportion of CD8⁺CD27^–IFN-γ⁺ (p = 0.0105) and CD4⁺CD27⁺HLA-DR⁺CD38⁺ (p = 0.0077) T cells than fast responders at baseline. Receiver operating curve analysis of these subsets resulted in 80% sensitivity and 70 and 100% specificity, respectively (AUC of 0.82, p = 0.0156 and 0.84, p = 0.0102).

Conclusion

Our pilot data show reductions in expression of T cell activation markers were seen with treatment, but this was not associated with fast or slow sputum conversion at 2 months. However, baseline proportions of activated T cell subsets are potentially predictive of the subsequent speed of response to treatment.

Assessing the preparedness of primary healthcare facilities during a cholera outbreak in Kinshasa, Democratic Republic of the Congo, 2018

OBJECTIVE

During the 2017-2018 cholera outbreak in Kinshasa, many patients initially reported to primary healthcare centers (HCs) before being transferred to the nearest cholera treatment centers. This study aims to assess the level of preparedness of HCs in responding to cholera outbreaks.

STUDY DESIGN

Descriptive cross-sectional survey.

METHODS

We conducted a descriptive cross-sectional survey in 180 of 374 primary HCs in Kinshasa. We collected data on 14 cholera preparedness criteria and described their prevalence among HCs. We used logistic regression to assess the association between each preparedness criteria and previous reporting of cholera cases by HCs.

RESULTS

The median number of preparedness criteria met by HCs was 5 [range: 0-11]. Five percent (n = 9) of HCs [95% confidence interval (CI): 2.3%-9.3%] met at least 10 criteria. HCs that previously reported ≥3 cholera cases were less likely to meet the criteria for 'presence of an isolation unit' (adjusted odds ratio [aOR]: 0.12; 95% CI [0.03-0.61]) and 'availability of sufficient quantity of chlorine' (aOR: 0.13; 95% CI [0.02-0.64]).

CONCLUSIONS

Despite past experience of cholera cases, health facilities in Kinshasa exhibit a low level of cholera preparedness. There is a need to prioritize the reinforcement of the preparedness of primary HCs to prevent future cholera outbreaks.

Analysis of cellular and soluble profiles in QuantiFERON nonconverters, converters, and reverters in the Gambia

Background

Tuberculosis (TB) is the leading cause of death from a single infectious agent worldwide. The immune system is capable of clearing the pathogen before establishment of latent infection but the mechanisms for this are not yet understood.

Methods

This study analysed highly exposed household contacts (HHC) of TB index cases who were categorised according to QuantiFERON (QFT) results at recruitment and 6 months. Seventeen (17) QFT nonconverters, 14 QFT converters, 18 QFT reverters and 18 latent TB infection (LTBI) were analysed. Supernatants generated following QFT stimulation at both time‐points were analysed using a 64‐plex cytokine array. Flow cytometry was performed on QFT converters and nonconverters at baseline only.

Results

Interleukin‐2 (IL‐2), IL‐5, IL‐13, APRIL, IL‐17A, IP‐10, MIP‐1ß, sIL‐6rb, OPN, and sTNFR2 were all significantly higher in the QFT converters compared with nonconverters at baseline. Levels of interferon‐α2 (IFN‐α2) and IL‐2 were significantly lower in QFT reverters compared with nonconverters at baseline. Analysis of Ag‐specific IL‐2 levels resulted in an area under the curve (AUC) of 0.93 (95% confidence interval [CI], 0.84‐1.00) for QFT converters compared to nonconverters and an AUC of 0.80 (0.65‐0.95) for QFT reverters compared with LTBI. Purified protein derivative (PPD)‐specific CD4 + CD26 + IFN‐γ + cells were significantly increased (P = .0007) in QFT nonconverters compared with QFT converters at baseline.

Conclusions

Our results provide insight into the underlying mechanisms of resistance to sustained Mycobacterium tuberculosis infection.

PO 8485 INTERFERON GAMMA RESPONSE KINETICS IN TUBERCULOSIS PATIENTS AND HOUSEHOLD CONTACTS IN THE GAMBIA

Background

Methods which use Mycobacterium tuberculosis (Mtb)-specific antigens to measure IFN-γ responses (IFN-γ release assays (IGRA)) have been useful in detecting Mtb infection in exposed individuals. We assessed infections in TB cases and their exposed household contacts (HHC) using an in-house optimised IGRA, the QuantiFERON-TB Gold in Tube (QFT-GIT) and QFT-Plus (QFT+).

Methods

For the in-house IGRA, we analysed 266 active TB patients and 759 HHC (256 tuberculin skin test-positive and 503 test-negative, TST+ and TST- respectively) at baseline and 6 months. In a separate study we assessed QFT-GIT and QFT-plus responses using samples from 72 TB cases and 69 HHC at baseline. QFT-GIT has 3 Mtb-specific antigens: ESAT6, CFP10 and TB7.7 while QFT-plus has long and short peptides of ESAT-6 and CFP-10, designed to induce CD4+ and CD8+T cell responses respectively.

Results

IFN-γ responses were lowest in TST- compared to both TST+ and TB patients at baseline (p<0.0001 for both), with 32% IGRA-positive compared to 76% and 73%, respectively using in-house IGRA. HHC sleeping in the same room with TB patient had a significantly higher IGRA conversion rate by 6 months compared to those sleeping further away (p=0.0004). We also observed a significant decline in IGRA IFN-γ levels by 6 months of TB treatment (p<0.0001). Among QFT-positive TB patients, smear-positive was 57% and culture-positive was 62%. The IFN-γ concentration between TB1 and TB 2 was similar, while, QFT-GIT had a significantly higher response than TB 1 and TB 2 for both TB patients (p=0.003) and HHC (p=0.0005).

Conclusion

Our findings show that IGRA conversion is significantly increased in HHC with highest exposure but that IGRA -positive cannot predict risk of progression to active TB. We also found that QFT-GIT was quantifiably better than QTF-plus in our setting, limiting the ‘grey zone’ of indeterminate results.

M. tuberculosis T Cell Epitope Analysis Reveals Paucity of Antigenic Variation and Identifies Rare Variable TB Antigens

Pathogens that evade adaptive immunity typically exhibit antigenic variation. By contrast, it appears that although the chronic human tuberculosis (TB)-causing pathogen Mycobacterium tuberculosis needs to counter host T cell responses, its T cell epitopes are hyperconserved. Here we present an extensive analysis of the T cell epitopes of M. tuberculosis. We combined population genomics with experimental immunology to determine the number and identity of T cell epitope sequence variants in 216 phylogenetically diverse strains of M. tuberculosis. Antigen conservation is indeed a hallmark of M. tuberculosis. However, our analysis revealed a set of seven variable antigens that were immunogenic in subjects with active TB. These findings suggest that M. tuberculosis uses mechanisms other than antigenic variation to evade T cells. T cell epitopes that exhibit sequence variation may not be subject to the same evasion mechanisms, and hence vaccines that include such variable epitopes may be more efficacious.